Little Red Rover Firmware

Firmware for the ESP32-S3-MINI-1 built into the rover's body.

This project uses the Espressif IoT Development Framework (espIDF) read more.

Birds Eye View

Little Red Rover's firmware is responsible for three tasks:

1. Establishing Wi-Fi connectivity
2. Reading information from sensors (LiDAR, IMU, wheel encoders)
3. Writing commands to actuators (wheel motors)
4. Relaying sensor data and recieving commands over a TCP connection

Because all high level algorithms are run on the base station computer (see lrr_ros), the rover itself has very little control logic. Instead, it's optimized for network transmisison and reception.

API

The rover hosts a TCP server listening on port 8001. When connected to the rover's hotspot, the ESP32-S3 has the IP address 192.168.4.1, making the TCP server address 192.168.4.1:8001.

Send commands using the format defined in the protobuf schema messages.proto.

To recieve data, the client must first send a SubscribeRequest message with the relevant OutgoingMessageID. The rover will then begin sending data to that port.

TODO: update link on C++ PR merge.

Composite Technologies

FreeRTOS

The system is based on FreeRTOS, a realtime embedded operating system (RTOS). FreeRTOS provides scheduling and mutlithreading utilities that are crucial for running efficiently in an asynchronous networking environment.

NanoPB

In order for data to be transmitted over the network, it needs to be serialized appropriately. This project uses Google's ProtocolBuffers. Specifically, the firmware uses an embedded focused implementation of ProtocolBuffers called NanoPB.

Project Structure

• /main
  • lrr_main.cc: The firmware entry point. Initializes drivers.
• /components
  • /communication_stack
    • /wifi_manager:
      • Initializes wifi
      • Handles provisioning (connecting to Wi-Fi using remotely provided credentials)
      • Connects to Wi-Fi
      • Sets up NAPT so that users can connect to the internet through the rover
    • /socket_manager:
      • Multithreaded TCP server implementation
      • Manages multiple client connections, data subscriptions, and general network IO
  • /hardware_drivers
    • /battery:
      • Measures battery using the ADC
      • Telemeters battery level data
    • /drive_base:
      • Integrates encoder pulses using the ESP32-S3 pulse counter module (PCNT)
      • Drives PID control for the motors
      • Accepts joint state commands as JointCmd messages (see protobuf message definition)
      • Telemeters joint state information as JointState messages
    • /imu:
      • Reads data from the IMU over I2C
      • Telemeters IMU data as IMU messages
    • /lidar:
      • Reads data from the LD20 LiDAR over UART
      • Telemeters LiDAR data as LaserScan messages
    • /status_led:
      • Provides a function to set the status LEDs in response to system events

Development Environment

The /docker and /.devcontainer folder provide a devcontainer environment for development. The docker container uses privilaged mode to flash the ESP32-S3 over USB. The privilaged flag is not supported on MacOS or Windows, so this may not work for you.

Cross platform build instructions are a WIP.